That already happens now. Everywhere in the world legislators are constantly trying, and often succeeding, to push through legislation that is counter productive to the well being of society as a whole. Here's where it gets tricky though. Let's say that an engineer in Congress makes a great law about maintaining bridges. His heart is in the right place and the law, if implemented, would do a world of good when it comes to keeping our infrastructure safe. However, said engineer doesn't have a lot of experience in the legal world. As a result, there are a lot of problems with the way his bill is drafted that causes it to directly conflict with preexisting laws that involve infrastructure and government spending. It's quickly taken to court, shot down, and a bunch of time and money is wasted. He can try to push the law through again, but the first time around it just barely eeked out the votes needed. He won't stand a hope a second time. Now, let's flip it. Let's say a bunch of engineers have a great idea involving bridge maintenance. They collect their data and bring it to a group of interested congressmen to show them how not only will their idea make bridges safer, but save the government money in the long run. Those congressmen, being the clever law writers that they are, can write a solid, concrete bill that if passed into law can hold up to the scrutiny of the courts. In my head, this is how I see it working. Is that how it actually works in the real world? Hell if I know. I know jack all about politics. Maybe we could get someone in here who knows a thing or two about civics to lead this conversation in the right direction.
Poorly written bills don't tend to become law. There is a substantial behind the scenes process with legislative advisors (and lobbyists) who help draft the exact language. Lawmakers themselves are not the ones doing this, so they might as well actually understand the practical implications of what they're passing.
Well, I study Political Science I don't know if that counts. The reason I submitted the idea of having politicians be more than simply lawyers is because many have no background in the subjects they are overseeing, but even my suggestion is not enough to fix the problem. In most cases what happens is politicians don't actually write the laws. Its the lobbyists themselves that draft the laws, and then pass them on to the politician. In most cases the only way you are getting into a congressman or senators office is if you have a large enough following that could cause them an issue during elections. The other way to get into their office is if you or your company donate enough money to their campaign during elections. The money part has the best chance of getting you into the office though. In many cases the lobbyist, experts, and advisers are hired by a corporation with an agenda of their own. The politician really can't deny them access if their contribution to their campaign is solid enough out of fear this corp. donates to their opponent (which sometimes they do to hedge their bets). This causes the greatest number of issues, but something like that is hard to just wipe away. Some smaller more controllable issues are that many of these politicians don't even know what to look for when being presented these pieces of legislation. If they had some expertise it could maybe allow them to look at a piece of legislation more objectively, but that may not be the case with what I mentioned above. Also, to your examples. Why can't that one engineer congressman have a team of legal people to interpret his law for him into something viable? Again, I'm not saying they shouldn't be lawyers at all, but it wouldn't hurt to have people at least knowledgeable enough in a certain subject.
In general I agree with pretty much all your points, but I can't help but feel cynical that the political horse trading that goes on would effectively bar most experts from sitting on comities that they could bring insight to. What I think would be a more workable, but probably just as easily corruptible solution, would be lawmakers directly employing experts. This would hopefully make them more beholden to give good a advice instead of just following a lobbyist agenda, though I'm sure that's just wishful thinking on my part.